Gases may form in an engine crankcase when gases from engine cylinders bypass engine pistons and enter the crankcase during engine rotation. The gases can be combusted within engine cylinders to reduce engine hydrocarbon emissions via returning the crankcase gases to the engine air intake and combusting the gases with a fresh air-fuel mixture. However, the crankcase gases may include engine oil mist. If engine oil is combusted by the engine, engine oil consumption may increase. In addition, performance of exhaust gas after treatment devices may degrade when engine oil is combusted. Therefore, it may be desirable to separate oil from crankcase gases that are directed from the engine crankcase to the engine air intake.
Combusting crankcase gases via the engine cylinders may require a motive force to move the crankcase gases from the engine crankcase to the engine air intake. One way to provide motive force to move crankcase gases to engine cylinders is to pneumatically couple the output of an engine oil separator receiving engine crankcase gases with a low pressure region (e.g., vacuum) of the engine intake system (e.g., the engine intake manifold between engine cylinders and an engine throttle body). Vacuum can draw crankcase gases to engine cylinders, but vacuum may also act on engine oil separated from crankcase gases, thereby making it more difficult to return engine oil to the engine crankcase. The vacuum acting on the separated oil may be overcome by building oil head pressure. In other words, the weight of the column of oil can work against the vacuum and allow the separated oil to be returned to the engine crankcase. The oil head pressure may be provided via the weight of separated engine oil stored in a column. However, depending on the amount of vacuum supplied to move crankcase vapors to the engine air intake, an oil column of more than 9 cm. may have to be produced to overcome the vacuum moving the crankcase gases. An oil column as such can increase the height of an engine and help to degrade vehicle fuel economy since it may increase a vehicle's coefficient of drag.
In addition, separated oil may be returned to the engine sump to promote oil mixing and to ensure oil used throughout the engine is at a more uniform temperature. However, an oil return line or passage may have to utilize a portion of the engine structure that may be useful for other purposes (e.g., engine block stiffening or coolant passage area). Thus, the positive crankcase ventilation (PCV) oil return passage may compete with other engine elements and features for sought after engine structure.
The inventors herein have recognized the above-mentioned disadvantages and have developed an engine system, comprising: an engine cylinder block; a cylinder head coupled to the engine cylinder block; a cylinder head cover coupled to the cylinder head; a dipstick oil passage extending through the cylinder head cover, the cylinder head, and the engine cylinder block to an engine crankcase.
By integrating the dipstick passage with the PCV oil return it may be possible to more efficiently use engine structure while providing adequate oil head pressure to overcome engine vacuum that extracts crankcase gases. In one example, the PCV oil return passage may accept engine oil solely from an engine oil separator and extend from a cylinder head to the engine crankcase. Thus, the PCV oil return passage allows for oil head pressure to build within the passage so that engine vacuum can be overcome. Further, via accepting an oil dipstick, the PCV oil return passage may more efficiently utilize engine structure by providing increased functionality.
The present description may provide several advantages. In particular, the approach may provide increased functionality so as to better utilize engine structure via increased PCV oil return passage functionality. In addition, the approach can leverage the length of the PCV oil return passage to provide additional oil head pressure so that oil from an oil separator may be continuously returned to the engine oil sump even during conditions of higher engine manifold vacuum.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.